Pomeranchuk, Isaak Iakovlevich

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POMERANCHUK, ISAAK IAKOVLEVICH

(b. Warsaw, Poland, 20 May 1913; d. Moscow, U.S.S.R., 14 Decembr 1966)

physics.

Pomeranchuk’s father, lakov Isaakovich, was a chemical engineer; his mother, Amalia Davydovna, was a dentist.

In 1918 the family moved from Warsaw to Rostovon-Don in southern Russia, and later to the Don coal region (Donbass). There Pomeranchuk studied at a two-year “factory” school; after graduating he began to work, in 1929, in a chemical plant. In 1931 he enrolled in the Institute of Chemical Engineering at Ivanovo, and the following year transferred to the Faculty of Physics and Mechanics of the Leningrad Polytechnical Institute, from which he graduated in 1936.

In 1935 Pomeranchuk was sent to Kharkov, where he prepared his thesis at the Ukrainian Physical-Technical Institute under the guidance of Lev Davidovich Landau. Pomeranchuk’s subsequent scientific activity was closely connected with Landau and his school. His first two papers, published in 1936, were written with Landau; of his some 130 papers, eight were written jointly with Landau, and many others were first discussed with him (“passed through the teacher”, as their colleagues used to say).

During the first period of his scientific career, Pomeranchuk often changed his work place: the Ukrainian Physical-Technical Institute (1936–1937), Leningrad University (1938–1939), the Leningrad Physical-Technical Institute (1939–1940), the P. N. Lebedev Institute of Physics in Moscow (1940–1943), and again the Leningrad Physical-Technical Institute (1948–1949). He was also associated with the Kurchatov Institute of Atomic Energy (1943–1946) and the Alikhanov Institute of Theoretical and Experimental Physics (1946–1948); at the latter, after his return from Leningrad, he was head of the theoretical department from 1949 until his death.

In 1953 Pomeranchuk was elected corresponding member, and in 1964 full member, of the U.S.S.R. Academy of Sciences. He was awarded the State Prize in 1950 and 1952. He organized a number of theoretical groups at the Institute of Technical and Experimental Physics, at the Kurchatov Institute of Atomic Energy in Moscow, and at the Joint Institute for Nuclear Research in Dubna. For two decades he served as a professor at the Moscow Institute for Engineering Physics, in the same department as M.A. Leontovich and I.E. Tamm.

Pomeranchuk’s scientific activity embraced a wide range of theoretical physics. He liked to work with his pupils and colleagues; he wrote a great number of publications jointly with A.I. Akhiezer, who was Landau’s first pupil, as well as with V.B. Berestetskii, Lev Borisovich Okun’ (Pomeranchuk’s pupil), and Vladimir Naumovich Gribov from the Physical-Technical Institute in Leningrad (the last series of papers was written between 1962 and 1966).

During the late 1930’s Pomeranchuk was mostly involved in solid state physics. In 1936 he and Landau showed that the interaction of conduction electrons leads to a quadratic law of the temperature dependence of the resistivity of pure metals at low temperatures (in contrast with the law of T5 [R∼T5 ] determined by scattering from thermal oscillations of a lattice). The paper constituted his candidate thesis, defended in 1936 after a year and a half of postgraduate work with Landau’s group. This work was complemented in a 1958 paper, in which Pomeranchuk took into account the role of isotopes entering the lattice of a pure (free of admixtures) crystal. Because of the differences in mass change, the lattice oscillations change, which in turn directly influences electrical resistivity of a metal at low temperatures.

In 1937 Pomeranchuk turned his attention to neutron physics and created the theory of elastic and nonelastic scattering of slow neutrons by nuclei bound in a crystal: in particular he studied in detail the case of scattering in crystal hydrogen. He returned to that problem in the late 1940’s, in a paper written with Akhiezer, in which they showed that the interaction of neutrons with ferromagnetics and paramagnetics demonstrates a close analogy with common optics (the refraction coefficient and the angle of total internal reflection being dependent on the orientation of the neutron’s spin).

A number of papers that formed Pomeranchuk’s doctoral dissertation (defended in 1941) are devoted to the phonon theory of heat conduction of dielectrics for a wide range of temperatures. Here he took into account anharmonic effects and demonstrated the necessity of calculating multiphonon interaction (of order higher than 3). He also included in his analysis other mechanisms of phonons’ scattering, such as admixtures, reflections from the crystallites’ walls, and centers of elastic deformations. Pomeranchuk showed that in this “dirty” (Wolfgang Pauli’s expression) science one might obtain meaningful and far-reaching results.

Of great importance for Pomeranchuk’s scientific biography is a series of his applied works dealing with the physics of nuclear reactors. He began to be involved in this field in 1943, when he became the head of a research team in charge of the design of a nuclear reactor. With Igor Vasil’evich Kur-chatov, Pomeranchuk developed the theory of “exponential experiments.” He and Isai lzrailevich Gurevich then postulated the necessity of hetero-geneous deployment of uranium blocks within the reactor’s active zone and formulated the theory of resonance absorption of neutrons in that system.

Pomeranchuk published other papers on nuclear reactors, and is rightly considered the founder of the Soviet general theory of reactors.

Several papers written with Akhiezer are devoted to the scattering of neutrons in liquid helium. In a paper on liquid helium written with Landau in 1948, it was shown that any particle—be it atom or molecule—in a superfluid helium (including isotopes of He4) can participate in the normal, but not superfluid motion. In a 1950 paper on the theory of liquid He3 (tritium), Pomeranchuk developed the qualitative theory of quantum liquids with Fermi energy spectrum and predicted the “Pomeranchuk effect,” that is, the existence of a minimum melting point for He3 on the pT plane (this minimum was later confirmed experimentally). In the same paper he demonstrated the theoretical possibility of reaching ultralow temperatures by adiabatic solidification of liquid He3.

During the period 1946-1949, Pomeranchuk obtained important results (with Lev Andreevich Art-simovich and Dmitrii Dmitrievich Ivanenko) on synchrotron radiation. In particular the authors showed that this radiation determines most of the losses associated with acceleration of electrons in betatrons and synchrotrons. A paper written with Landau presented a complete theory of brems-strahlung. Pomeranchuk also achieved significant results in papers devoted to the spectra of positronium and to the mu-meson atom.

A large number of Pomeranchuk’s papers dealt with quantum field theory, the physics of strong interactions, and high-energy physics. In papers written in 1956, partly in collaboration with Okun,’ the equality of cross sections of elastic and nonelastic scattering of π+, πand π0 mesons by nucleons was obtained. The analysis of dispersion relations (1958) showed that for high energies the complete effective interaction cross section of a particle and an antiparticle with the same target tends toward the same limit as the collision energy increases (Pomeranchuk theorem). This result has been confirmed in the experiments on the most powerful accelerators.

In the last series of papers, written between 1962 and 1966 in collaboration with Gribov, Pomeranchuk further developed the method of complex momenta, first suggested by Tullio Regge, for a study of asymptotic behavior of cross sections of various processes in the high-energy limit. In these papers, based on the investigation of behavior of the “Pomeranchuk poles,” he proved important theoremes concerning the relative values of cross sections for various processes of scattering and in relation to the effect of concentration of Regge poles and the branching points on the plane of complex momenta.

Despite a grave illness, Pomeranchuk continued his intensive work even after being hospitalized. His last paper (on asymptotic behavior of the complete cross section of the electron-positron annihilation in argon) was completed two days before his death. A number of papers that he discussed with his colleagues during the last month of his life were published posthumously, including a paper on weak interactions (the limitation of the rate of growth of cross sections for the [v, e ] process).

Pomeranchuk’s friend V. B. Berestetskii said about him: “His work was his highest enjoyment. He was tireless, Physics was his life. He did not understand how one could spare time for anything else.”

BIBLIOGRAPHY

I. Original Works. Pomeranchuk’s works are listed in Uspekhi fizicheskikh nauk, 92 , no. 2 (1967), 360–365, and in his Sobranie nauchnykh trudov (Collected scientific works), III (Moscow, 1972), 411–416. The most important papers are “O svoistvakh metallov pri ochen nizkikh temperaturakh” (On the properties of metals at very low temperatures), in Zhurnal eksperimentalnoi i teoreticheskoi fiziki, 7 (1937), 649, written with Lev D. Landau; “On the Thermal Conductivity of Dielectrics,” in Physical Review, 60 , no. 11 (1941), 820–821; “On the Heat Conductivity of Salts Used in the Magnetic Cooling Method,” in Journal of Physics of the USSR, 8 , no. 4 (1944), 216, written with A. I. Akhiezer; “O maksimalnoi energii, dostizhimoi v betatrone” (On the maximum energy reachable in the betatron), in Doklady Akademü nauk SSSR, 44 (1944), 343, written with Dmitrii D. Ivanenko; “lzluchenie bystrykh elektronov v magnitnom pole” (The radiation of fast electrons in the magnetic field), in Fizicheskii zhurnal, 9 , no. 4 (1945), 267, written with Lev A. Artsimovich; “O rasseianii neitronov s energiei neskolko gradusov v zhidkom gelii II” (on the scattering of low-energy electrons in helium-II), ibid., 9 , no. 6 (1945), 461, written with A. I. Akhiezer: Nekotorye voprosy teorii iadra (Some problems of the nuclear theory; Moscow, 1948; 2nd ed., 1950), written with A. I. Akhiezer; “O dvizhenii postoronnikh chastits v gelii II” (On the motion of foreign particles in liquid helium-II), in Doklady Akademü nauk SSSR, 59 (1948), 669–670, written with Lev D. Landau; “K teorii zhidkogo3He” (On the liquid3He theory), in Zhurnal eksperimentalnoi i teoreticheskoi fiziki, 20 (1950), 919–924; “Asymptotic Behaviour of Annihilation and Elastic Scattering Processes at High Energies,” in Nuclear Physics, 33, no. 3 (1962), 516–523, written with Vladimir N. Griboy; “Regge Poles and Landau Singularities,” in Physical Review Letters, 9 , no. 5 (1962), 238–242, written with Vladimir N. Gribov; and Sobranie nauchnykh trudov (Collected scientific works), V. B. Berestetskii, ed, 3 vols. (Moscow, 1972).

II. Secondary Literature. V. N. Berestetskii, “lsaak lakovlevich Pomeranchuk,” in Uspekhi fizicheskikh nauk, 92 , no. 2 (1967), 355–365; I. N. Golovin, I. V. Kurchatov (Moscow, 1972), 53–54, and L. I. Lapidus, “Isaak lakovlevich Pomeranchuk,” in Priroda (1967), no. 12, 51.

V. J. Frenkel